Thermally-assisted magnetic recording systems are receiving attention as a technology suitable for the next generation of high-density hard disk drives. Thermally-assisted magnetic recording is based on directing light onto a media to raise the temperature of the media. A laser diode provided in the head serves as a light source. High-frequency laser modulation stabilizes the emission intensity of a laser diode.
Methods of high-frequency laser modulation include a method comprising the use of a self-pulsating laser diode and a method based on drive current modulation. The former, which is suitable for use with optical recording technologies, such as compact disks and digital video discs, affords an internal laser diode modulation of several hundred MHz even when drive is based on the use of a direct current laser diode. However, this method is not suitable for use with hard disk drives because the bandwidths used by the hard disk drives reach several GHz. Accordingly, a system based on drive current modulation is used therewith.
In systems based on drive current modulation, a prescribed temperature of the media is established when bit switching occurs. Otherwise, displacement of the boundary position between one bit and another bit occurs accompanying a large change in the hot spot on the media. Accordingly, for systems based on drive current modulation, a data-synchronized laser current pulse is generated.
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